There's no shortage of YouTube playlist generators out there, but most of them are a bit funky to use. YouTube Related Music is simple and looks great.

To use YouTube Related Music, you simply need to type in the name of a song, select the video you want, and the webapp generates a playlist. You can get rid of the next upcoming song, but you can't reorder the rest of the playlist. YouTube Related Music uses the same related API that YouTube itself uses, so its results are best suited for more popular music. Still, as an endless player that's free of ads, it's another great option to add to your music discovery toolkit.